1. Field of the Invention
The present invention relates to the field of display techniques, and in particular to a flexible thin film transistor (TFT) substrate and manufacturing method thereof.
2. The Related Arts
As the display technology progresses, the liquid crystal display (LCD) and organic light-emitting diode (OLED) displays are widely used because of the advantages of high display quality, low power-consumption, and thinness, in applications, such as mobile phones, TV, PDA, digital cameras, notebook PC, desktop PC, and so on consumer products and becomes the mainstream of the display device.
Most of the LCDs on the current market are of backlight type, which comprises an LCD panel and a backlight module. The operation theory behind LCD is to inject the liquid crystal (LC) molecules between two parallel glass substrates, and a plurality of vertical and horizontal tiny wires is disposed between the two parallel glass substrates. By applying a driving voltage between the two substrates to control the rotation direction of the LC molecules to refract the light from the backlight module to generate the display on the screen.
The current LCD usually comprises: a color filter (CF) substrate, a TFT substrate, an LC sandwiched between the CF substrate and the TFT substrate, and a sealant. The manufacturing process usually comprises: an array process at the beginning (i.e., thin film, lithography, etching and stripping), followed by a cell process in the middle (attaching TFT substrate and CF substrate), and then an liquid crystal module (LCM) process at the end (pressing driving integrated circuit (IC) and printed circuit board (PCB) together); wherein the array process is to form the TFT substrate to enable controlling the motion of LC molecules; the cell process is to add LC molecules between the TFT substrate and the CF substrate; and the LCM process is to integrate the driving IC and the PCB to drive the rotation of the LC molecules and display the image.
The OLED display is a flat panel display device and provides the advantages of simple manufacturing process, low cost, low power-consumption, active light-emitting, high emission efficiency, quick response time, thinness, wide operation temperature range, and capability to realize flexible display and large-area full-color display, as well as the capability to match driving IC, and is regarded as the most promising display technology.
An OLED typically comprises a substrate, an anode provided on the substrate, a hole injection layer (HIL) provided on the anode, a hole transport layer (HTL) provided on the hole injection layer, a light-emitting layer (EML) provided on the hole transport layer, an electron transport layer (ETL) provided on the light-emitting layer, an electron injection layer (EIL) provided on the electron transport layer, and a cathode provided on the electron transport layer. The theory of light-emission of OLED display the carrier injection and recombination for the semiconductor materials and organic light-emitting materials under the driving of the electric field. Specifically, the OLED display usually adopts the ITO pixel electrode and the metal electrode as the anode and the cathode. Under the driving of a certain voltage, the electron and the hole are respectively injected from the cathode and the anode into the electron transport layer and the hole transport layer respectively; and the electrons and the holes migrate through the electron transport layer and the hole transport layer respectively to the light-emitting layer to meet in the light emitting layer to form excitons and to excite the light-emitting molecules, which in turn emit visible light by radiation relaxation.
The driving types of OLED can be divided, according to the driving method, into the passive matrix OLED (PMOLED) and active matrix OLED (AMOLED), i.e., the direct addressable type and thin film transistor (TFT) addressable type, wherein the AMOLED provides the advantages of pixels arranged in an array, self-luminous, and high luminous efficiency and is commonly used for high definition large-size display.
The TFT is the main driving component of the known LCD and AMOLED display, and is directly linked to the development direction of high-performance panel display. The flexible TFT substrate has a wider application potential than the known TFT substrate, especially in the smart devices. However, the flexible TFT substrate manufactured by directly applying known TFT substrate manufacturing method to the flexible TFT substrate suffers the shortcomings of prone to broken wires, TFT component peeling and light leakage.